Apparatus for making froth



D. L. GlBsoN ET AL 3,322,664

APPARATUS FOR MAKING FROTH Filed Nov. 26, 1963 GS b Z INVENTORS. @ann/25 L. Gibson BY Doug/05 5. C/'i/'S/ro/m 3,322,684 APPARATUS FOR MAKING FROTH Dennis lL. Gibson and Douglas S. Chisholm, Midland,

Mich., assignors to 'Ille Dow Chemical Company, Mldland, Mich., a corporation of Delaware rFiled' Nov. 26, 1963, Ser. No. 326,017 8 Claims. (Cl. 252-359) This invention relates to mixing apparatus and particularly to a method and apparatus for making froths.

The production of froths, e.g., the dispersion `bubbles Of gas in a liquid, in which the size of the bubbles and their number and distribution in a liquid may readily be controlled has been a desirable objective for a considerable time.

Accordingly, a principal object of this invention is to provide an improved apparatus for making a froth.

Another object of this invention is to provide an improved, simpler apparatus for making a froth.

A further object of this invention is to provide an improved, more economical apparatus for making a froth.

In accordance with this invention gas is passed through a porous plate and into a chamber into which liquid is supplied wherein a rotating impeller whose blades are disposed in close spaced relationship with respect to the porous plate shears off gas bubbles as the gas leaves the porous plate, mixes the bubbles with the liquid in the chamber, and discharges the resulting froth from the peripheral part of the chamber.

Cell size and number is varied by changing the gas iiow rate, impeller rotation rate, rate at which liquid is supplied to the chamber, the spacing between the impeller blades and the porous plate, and the size of the pores in the porous plate.

The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the aecompanying drawings, in which:

FIG. 1 is an exploded view of froth making apparatus in accordance with this invention;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. l; Y

FIG. 3 is a sectional view taken along the line 3-3 of FIG. l;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. l; and

FIG. 5 is a side elevational View of the apparatus shown in FIG. 1.

Referring to the drawings, and particularly -to FIG. 5, there is shown froth making apparatus, indicated generally by the numeral 10, in accordance with this invention. The apparatus comprises a gas and liquid inlet member 12, to which the individual gas inlet 14 and liquid inlet 16 are coupled, a housing 18, and driving motor 20.

Referring now to FIGS. l, 2, 3, and 4, it may be seen that the housing 18 comprises an input section 22, an output section 24, and a gasket spacer section 26 and a porous plate 28, and a gasket 30 sandwiched between the sections 22, 24.

The housing section 24 is a generally shallow cup shaped member. Its interior side walls 32 are substantially cylindrical and its end wall 34 which is substantially perpendicular to the side Walls, the side and end walls defining a cylindrically shaped cup. A bladed impeller 36 whose blades 44 extend almost to the side walls 32 is coupled to a longitudinally disposed shaft 38 which extends through a bore 40 in the end 42 of the housing section 24. The shaft 38, passing through the bearing 46, may be the shaft of the motor 20, as shown, or other suitably journaled shaft which is adapted to be rotated by other means (not shown). Threaded bores 3S, disposed 3,322,634 Patented May 30, 1967 near the periphery of the section 24, accommodate the bolts 52 when the device is assembled.

The four blades 44 of the impeller 36, disposed within the section 24, extend substantially perpendicularly with respect to the longitudinal axis of the shaft 38 and are disposed at an angle of approximately degrees with respect to each other. The length of the vblades 44 is such that the blades extend from the shaft 38 to near the side wall 32. Steel is commonly the structural material used in making the impeller, although other materials which do not react with the materials fed through the device may be used.

An output bore 45 extends between the peripheral part of the section 24 and the interior of the section.

The gasket 30 and the spacer gasket 26 are each annular in form and have bores 48, 50, respectively, `through which the bolts 52 pass when the device is assembled.

The porous plate 28 is disc-like in form and has pores having a mean diameter of l5 microns. The plate 28 has a bore 54 which is aligned with the longitudinal axis of the device (axis of shaft 38, too). The bore 54 is counterbored on the side facing the impeller. The plate 28, like the spacer-gasket 26 and gasket 30, has bores 56 adjacent to its peripheral part.

The input vsection 22 is, generally, an axially disposed bore 58 extending therethrough and an axially disposed boss 60 on the exterior side 62 of the section. The bore 58 has a flared counterbored part 64 on the interior side 66 of the section. Bores 68, disposed near the peripheral part of the section 22, accommodate a thick plate having ythe bolts 52.

The gas and liquid inlet member 12 is, in effect, a T type pipe coupling in which the gas line 14 is coupled to the transverse segment 7l) of the coupling and the liquid inlet member 16 is coupled to one of the in-line segments of the coupling 12. The member 16, smaller in outer diameter than the diameter of the bore which extends through the coupling 12, extends through and beyond the coupling 12. The length of the member 16 which extends beyond the coupling 12 is such that, when the device is assembled, the member 16 extends into the bore 54 of the porous plate 28.

A larger diameter conduit 72 is coupled between the coupling 12 and the bore 58 of the input section 22, the diameter of the conduit 60 being such that it surrounds and is spaced from the member 16.

In operation, liquid is pumped through the inlet tube 16 which extends through or at least into the bore 54 in the porous plate 28, and into a chamber which is bounded on one end by the porous plate 28 and on the other end and sides `by the housing section 24 and, to a small extent, by the gasket 30.

The chamber just described, with the impeller 36 disposed therein, receives water, other liquid or liquid miX- ture directly from Ithe inlet tube or conduit 16. The irnpeller 36, coupled to the shaft 38, is rotated by means of the motor 20, which is attached to a suitable base 79 and is energized through the electrical leads 74, 76, `the switch 78, and speed control 80. Gas enters the apparatus through the inlet tube 14, the inlet member 12 and the space between the tube 16`and the walls of the conduit 72 and the bore 58. The gas then enters the space defined by the interior side 66 of the section 22, the gasket spacer 26, and the surface of the porous plate 28 which faces the surface 66 of the section 22.

When the gas pressure is in excess the chamber containing the impeller 36, gas permeates the porous plate 28 and becomes mixed with the liquid in the impeller containing chamber. The spacing between the porous plate 28, made of sintered stainless steel, for eX- ample, and the blades 44 of the impeller should be small, less than one-fourth inch, for example, and preferably of the pressure in smaller in order to promote more eflicient shearing of air bubbles on? the plate 28. Porous ceramic or other material having suitable physical characteristics and which is compatible with the liquid and gas may be substituted for stainless steel in the porous plate 28.

The mean diameter of the pore-s in the porous plate 28 should be between 5 and 165 microns. Fine pores require a higher pressure drop across the plate than coarse pores. The thickness of the plate 28 is such that it will maintain a xed position during operation. The plate 28 may be lmade of steel, other metal, or vitreous material, for example. In one apparatus made in accordance with this invention and used for experimental purposes, the thickness of the plate 28 is .040 inch, the mean diameter of the pores is microns, and the diameter of the impeller is 4 inches, the blades being in the form of two intersecting bars having their longitudinal axes in the same plane and oriented 90 degrees apart. The motor 20 is a series wound motor having a maximum speed of about 3,600 r.p.m. under loaded conditions.

When a 1 percent solution, alkyl benzene sulfonate and water, for example, but no gas, was passed through the above apparatus, the stream emerging from the apparatus was slightly turbid in appearance and was scattered in a lnonuniiorm flow pattern.

The introduction of a small amount of air through the plate 28 eliminated the non-uniformity of the stream emerging from the pump and imparted to it a creamy appearance.

As the rate of air flow was increased, the size of bubbles in the froth leaving the apparatus increased.

Finally, a rate of gas input was reached (liquid input rate constant during the tests described above) beyond which the flow from the apparatus became erratic with sporadic bursts of air and then froth.

At constant air-ow rate, increasing the speed of impeller rotation tends to decrease the size of the bubbles in the froth, but the effect is not so pronounced a-s that due to decreasing air-flow rate at a constant impeller speed.

The best operating conditions for individual devices in accordance with this invention, of course, will be de termined by the operator under actual working conditions.

This apparatus is useful for the manufacture of froth for flotation processes, re fighting foams, certain plastic foams, notably urethanes, which involve whipping action, or foams of glycerrhyzie acid, for example.

While impellers having solid blades have been heretofore described, the blades may be wires, as in a brush, for example, or may be serrated.

What is claimed is:

1. Apparatus for making froths, comprising an enclosed cylindrical chamber having opposed, spaced-apart, parallel end walls, side walls joining said end walls, a porous, parallel plate intermediate said end walls, means for introducing liquid into said chamber thru one end wall, means for withdrawing froth from said chamber, a rotatable bladed impeller being disposed on a shaft in said chamber with its blades generally closely adjacent to and coaxially aligned with said side walls, porous plate and other end wall, means for rotating said impeller, said one end wall comprising means including a cover plate spaced from said porous end wall for introducing gaseous foaming material into said chamber through the pores of said porous plate.

2. Apparatus in accordance with claim 1, wherein said means for introducing liquid into said chamber comprises a hollow conduit which is coupled to a bore extending through one of said end walls.

3. Apparatus in accordance with claim 1, wherein said means for withdrawing mixture from said chamber comprises a bore extending into said chamber from a peripheral part thereof.

4. Apparatus in accordance with claim 1, lwherein said means for rotating said impeller comprises a motor coupled to said shaft, said shafting extending through one of said end walls.

S. Apparatus in accordance with claim 1, wherein said porous wall has pores whose diameter range between 5 and microns.

6. Apparatus in accordance with claim 1, wherein said impeller blades are disposed not more than 1A inch from said porous wall.

7. Apparatus in accordance with claim 1, wherein said porous wall is made of sintered stainless steel.

8. Apparatus in accordance with claim 1, wherein said porous wall is made of ceramic material. 

1. APPARATUS FOR MAKING FROTHS, COMPRISING AN ENCLOSED CYLINDRICAL CHAMBER HAVING OPPOSED, SPACED-APART, PARALLEL END WALLS, SIDE WALLS JOINING SAID END WALLS, A POROUS, PARALLEL PLATE INTERMEDIATE SAID END WALLS, MEANS FOR INTRODUCING LIQUID INTO SAID CHAMBER THRU ONE END WALL, MEANS FOR WITHDRAWING FROTH FROM SAID CHAMBER, A ROTATABLE BLADED IMPELLER BEING DISPOSED ON A SHAFT IN SAID CHAMBER WITH ITS BLADES GENERALLY CLOSELY ADJACENT TO AND 